One thing to be aware of is sidebar panels aren't visible when in full screen mode... I don't know whether they can be made visible... but that's one advantage of a non-modal dialog over a panel - you can have it kept showing when the user switches to full screen mode.

I think we have to distinguish docking windows from _the_ side bar (menu:View>Sidebar). The data source browser and the "Pages" or "Slides" window in Impress/Draw appear in docking windows on top and on the left. The side bar appears always on the right side and has vertical "tabs", for hard formatting properties, navigator, stylist, galery.The Organon extension uses a docking window on the left (which annoyingly remains after the extension has been removed).Some docking windows seem to be fixed (Organon, data sources) whereas others can be switched to floating mode (navigator, stylist, pages, slides).

Please, edit this topic's initial post and add "[Solved]" to the subject line if your problem has been solved.Ubuntu 18.04, OpenOffice 4.x & LibreOffice 6.x

UNODialog Tools is a Python3 command-line tool which takes a .xdl file written in the Basic Dialog Editor and generates dialog code in PyUNO (Python) in order to create LibreOffice extension, sidebar extension or embed in ODF documents.